The present invention, generally, is related to the field of plastic material injection molding.
More specifically, the invention is related to a handling system for a plastic material injection molding machine comprising an arm for unloading plastic material articles from hollow cavities of a mold of the plastic material injection molding machine, wherein the hollow cavities are arranged in a first plane and the arm essentially moves within the first plane, a conveyor system moving within a second plane for transporting away the plastic material articles, and a transfer station arranged between the mold and the conveyor system for transferring the unloaded plastic material articles from the first plane to the second plane, the transfer station comprising a transfer plate for the plastic material articles and adapted to be moved along a predetermined trajectory from a first operational position within the first plane into a second operational position within the second plane.
A handling system of the afore-mentioned type is known in the art.
In conventional plastic material injection molding machines, the mold portions are displaced away from one another in a horizontal direction. For unloading the finished plastic material articles, an arm of a handling system is inserted into the gap between the two mold portions, wherein the trajectory of the arm conventionally extends under right angles relative to the trajectory of the mold portions. Gripper elements, for example suction heads, are arranged at the free end of the arm for unloading the finished injection-molded plastic material articles from the hollow cavities which now lie free. The handling system arm is then again retracted and transfers the articles to a transfer plate. The transfer plate is located outside the injection molding machine and has a receiving surface lying essentially in the same plane as the hollow cavities.
As the plastic materials have to be transported away there-after, it is conventional to utilize a conveyor belt running in a horizontal plane. In order to transfer the plastic material articles from the transfer plate onto the conveyor belt, the transfer plate is tilted about a horizontal axis in a forward direction so that the surface of the transfer plate that had been in a vertical orientation and had carried the plastic material articles is now tilted by 90xc2x0 downwardly so that the plastic material articles may now be transferred onto the conveyor belt.
The prior art handling system, hence, has the disadvantage that the transfer plate must be pivoted into an area where the arm is located. Therefore, the arm must first be displaced away out of the pivotal area of the transfer plate. This requires additional time so that the cycle time of the injection molding machine is increased.
It is, therefore, an object underlying the invention to improve a handling system of the type specified at the outset so that the afore-mentioned disadvantages are avoided. In particular, it shall become possible to effect the transfer from the transfer plate onto the conveyor belt such that it is not or almost not necessary to displace the arm before. By doing so, the cycle time may be reduced as compared with prior art handling systems and, hence, the productivity of the injection molding machine may be increased.
In a handling system of the type specified at the outset, this object is achieved in that the trajectory extends essentially outside the first plane.
The object underlying the invention is thus entirely solved because the trajectory of the transfer plate is positioned such that no collision with the arm is to be expected when the latter is in its retracted position in which the gripper elements on the arm are still in the position in which the plastic material articles had been transferred to the transfer plate. For, the plastic material articles are removed by the arm out of the hollow cavities in one direction and the trajectory of the transfer plate extends essentially in the opposite direction.
Considering that a separate displacement of the arm is no more necessary, in particular over relatively long distances as is the case in the prior art with relatively large transfer plates, the handling process is shortened which results in a reduction of the cycle time of the injection molding machine.
It is, therefore, possible to utilize the invention advantageously in connection with handling systems in which the first plane extends essentially vertically and, preferably, the second plane extends essentially horizontally, as known per se. Moreover, the invention may be utilized advantageously when the conveyor system comprises a conveyor belt.
If, according to another embodiment of the invention, the plastic material articles are arranged as groups within the first plane and are transferred in groups, the invention has further advantages. Namely, as has already been mentioned, in particular in connection with very large groups of plastic material articles and a corresponding plurality of hollow cavities within the mold, a correspondingly large transfer plate must also be provided. When the latter is pivoted in a conventional manner, the arm of the handling system must be driven far away in order to avoid collisions with the pivoted or tilted transfer plate.
In preferred embodiments of the invention, a transfer plate with a first rim thereof is arranged within the area of the second plane and, during the movement from the first into the second operational position, with its first rim is moved parallel to the second plane in a direction away from the first plane.
This measure has the advantage that the transfer plate ducks away downwardly and away from the first plane so that by means of this trajectory it is displaced on the one hand from the first into the second plane, i.e. preferably from its vertical into a horizontal position, on the other hand the trajectory of the arm is not intersected or only to a very small amount.
In connection with the afore-mentioned two embodiments, it is further preferred when the transfer plate is provided with a second rim opposite the first rim and the second rim, during the transition between the first and the second operational position, is guided essentially along the first plane.
This measure has the advantage to surely avoid that the transfer plate penetrates into the area of the first plane, i.e. into the trajectory of the arm, or, at least, that such penetration is reduced to an acceptable extent. Considering that according to this embodiment two opposite rims of the transfer plate are guided mechanically, another already mentioned advantage is that the plate is securely guided and there is no risk of canting same.
According to a modification of this embodiment, this trajectory may be realized in an advantageous manner in that the transfer plate is provided with a slide bearing in the area of the first rim, the slide bearing being adapted to be displaced along a slide rail extending parallel to the second plane.
This measure has the advantage that the afore-mentioned trajectory may be guaranteed and that the transfer plate during that movement is securely guided on its lower rim. A canting of the transfer plate during that sequence of movements is impossible.
In an additional or an alternative modification of the afore-mentioned embodiment, the transfer plate is only or also provided with a slide bearing in the area of the second rim, the slide bearing being adapted to be displaced along a slide rail extending parallel to the first plane.
In a first alternative thereto, the transfer plate, instead, is provided with a joint in the area of the first rim, the joint being adapted to displace along a circular trajectory of large radius extending essentially tangential to the second plane.
Correspondingly, in an inverted manner according to a second alternative the transfer plate may be provided with a joint in the area of the second rim, the joint being adapted to be displaced along a circular trajectory of large radius extending essentially tangential to the first plane.
In all these cases, a secure guide of the rims in the area of the first and of the second plane, respectively, is achieved. A precise longitudinal guide may then be achieved within the first and/or within the second plane by means of the guide rails. In the other case, this longitudinal guide is approximated by an arc of large radius. This alternative may be designed mechanically simpler, according to the specific situation.
According to further embodiments of the invention, the transfer plate is adapted to be moved between the first and the second operational positions by means of a rocker, wherein the rocker has a swivel point or joint arranged outside the transfer plate at least during a portion of the sequence of movements, a servo-mechanical actuator being provided engaging the swivel point or joint.
This measure has the advantage that the entire sequence of movements may be effected by one single actuator without the necessity of utilizing a plurality of drives.
Insofar it is particularly preferred when the actuator is arranged in the area of the second plane, preferably below the second plane.
These measures have several essential advantages. On the one hand, a drive located at the bottom results in a smaller vertical dimension of the handling system. Moreover, it is particularly preferred in connection with applications under clean room conditions when any drive elements are located within the lower portion of the installation. This is because clean rooms conventionally utilize a special air flow system, namely a so-called laminar flow system, in which the air flows from the ceiling downwardly to the floor of the room in order to dispose of any particles within the room. If in such a situation drive elements are positioned above the conveyor, it may happen that particles are generated through abrasion within the drive which are then taken along by the laminar flow and may, hence, deposit on the conveyed articles. This will be avoided when the drive elements are located below the conveyor or at least within the same vertical position as the conveyor. Moreover, when the drive elements are located at a low position, a mechanically more stable construction of the installation may be achieved and, simultaneously, a better access to the drive elements.
The advantages specified before of course hold also true in case that the drive elements for the arm of the handling system are also positioned below the conveyor.
It should further be mentioned at this instance that the afore-explained considerations of course also apply for a case in which, in an inverted manner compared to what was described before, articles are taken away from a conveyor belt and, by means of a handling system, are inserted into hollow cavities of the mold. Such a situation prevails, for example, when the plastic material articles shall be provided with certain inserts or parts, for example with reinforcing elements, pins, hinges or the like or, in the case of the production of socalled xe2x80x9csmart cardsxe2x80x9d with electronic circuits, antennas or similar elements. In that situation, the sequence of movements is just inverted as compared to what was described above, however, the described advantages are the same.
The actuator is preferably configured as a piston-and-cylinder unit, however, it goes without saying that also other actuators may be used, for example motorized actuators.
For what concerns the points of engagement of the actuator, two alternatives are encompassed by the invention.
In a first alternative, the actuator is linked to a stationary swivel point.
This measure has the advantage that a simple construction is achieved. However, the actuator must effect a relatively large stroke of displacement so that it might be necessary under certain circumstances, when a piston-and-cylinder unit is used, to select a telescope cylinder.
In an alternative, however, in which the transfer plate on at least one rim thereof is guided within a slide rail extending parallel to one of the planes by means of a slide bearing and the slide rail is adapted to be displaced parallel to the plane, the actuator may be linked to the displaceable guide rail.
This measure has the advantage that during the extension and the retraction of the actuator the slide rail being longitudinally movable is also displaced so that a complex sequence of movements is generated which, however, has the advantage that it requires only a limited space. Therefore, the handling system only requires a small space within the installation and the actuator itself needs only to effect a relatively small stroke. When a piston-and-cylinder unit is used, it is sufficient to use a simple piston and no telescope cylinder at all.
Further advantages will become apparent from the description and the enclosed drawing.
It goes without saying that the features mentioned before and those that will be explained hereinafter may not only be used in the particularly given combination but also in other combinations or alone without leaving the scope of the present invention.